As mobile communications develop, M2M (Machine To Machine, machine to machine) communication emerges. Compared with previous H2H (Human to Human, human to human) communication, M2M communication supports a much larger number of terminals, which is roughly estimated to be 50 billions, about 10 times the number of H2H communication terminals. For example, in a currently popular smart grid, the number of electric meters may reach 100 thousand in a cell.
The smart grid is one of relatively practical M2M applications. To optimize electric energy allocation, grid terminals are required to report data periodically. The huge number of grid terminals makes it infeasible to page terminals one by one for triggering data reporting. A group call in clustering naturally becomes a choice for optimization. A group call may reduce the paging load. However, if in-group terminals receive a group call message at the same time, they may initiate dense access within a short time, causing access channels of a RAN (Radio Access Network, radio access network) to be overloaded. Moreover, massive access of multiple groups may also cause signaling overload on a CN (Core Network, core network).
At present, a solution has been proposed to divide terminals in a group into more subgroups and initiate group calls based on subgroups to reduce the load or overload on a core network. However, the disadvantage of this solution lies in that: this solution not only requires processing resources for maintaining the subgroups, but also consumes additional signaling and processing resources for changing subgroup configurations.